Pilot light device for enclosures of electrical equipment



1962 D. .1. ARNEBERG ETAL ,05

PILOT LIGHT DEVICE FOR ENCLOSURES OF ELECTRICAL EQUIPMENT Filed March 8, 1961 3 Sheets-Sheet l IUNVENTORS. DON d: flE/VEEEE'G BY JOSEPH J 63085415 Oct. 16, 1962 D. J. ARNEBERG ETAL 3,059,231

PILOT LIGHT DEVICE FOR ENCLOSURES OF ELECTRICAL EQUIPMENT Filed March 8, 1961 3 Sheets-Sheet 2 3 DON JZWw F76. 3 7 By JOSEPH J fi/BBLE United States Patent i 3,059,231 PILOT LIGHT DEVICE FOR ENCLOSURES OF ELECTRICAL EQUIPMENT Don J. Arneberg and Joseph J. Gribble, Milwaukee, Wis.,

assignors to Square D Company, Park Ridge, 111., a corporation of Michigan Filed Mar. 8, 1961, Ser. No. 94,358 Claims. (Cl. 340-381) This invention relates to a pilot light device for enclosures of electrical equipment, and particularly for enclosures which are designed to withstand the force of explosions occurring within the enclosure as a result of ignition of explosive gases therein by sparking or arcing of the contained electrical equipment and to prevent the ignition of explosive vapors in the atmosphere surrounding the enclosure by contact therewith of flashes of vapor, sparks, and arcs escaping from within the enclosure.

Typical of enclosures for this purpose are those containing switches operating at industrial or higher voltages and amperages, wherein explosive gases within the enclosure may be ignited by the arcs or sparks due to interruption of the circuit.

Frequently, it is desirable that pilot light devices be provided on the enclosures for indicating whether the equipment in the enclosure is operative or not. In View of the locations in which such equipment is used, it is desirable that the pilot light be readily visible for relatively long distances so that the danger of overlooking the improper functioning of the equipment will be reduced.

The present device is extremely rugged and durable and is arranged so that it can be connected to such enclosures by threaded engagement with the Wall of a small passage leading into the enclosure. It can be connected to a circuit within the enclosure by drawing the proper wires therefrom through the passage and connecting them to the unattached pilot device. After connection with the wires, it can be readily installed. When installed, it prevents the ingress into the enclosure of foreign matter and the flashing of any explosive gases or sparks through the irregular passage space defined by the threaded walls of the device and enclosure. The device itself is arranged so that sparks and gases cannot pass therethrough.

The pilot light device is provided with a lens which is of a shape to give its maximum visibility with a minmum diameter. The lens is efiectively guarded to protect it against accidental breakage.

The pilot light unit is arranged so that it can be installled and replaced readily, as also can the bulb, in event of burn out or breakage. Though it is readily installable and removable, it is arranged with a latch by which it can be latched in place so as to secure it against loosening or accidental detachment from the enclosure on which it is installed. The lens and its associated guard also may readily be removed as a unit, without interfering with the connections of the structure generally to the enclosure. The bulb also may be removed without disconnection of the device from the enclosure.

When the device is detached in its entirety from the enclosure, the sockets for the bulb can readily be removed and replaced.

Other advantages of the invention will become apparent from the following description wherein reference is made to the drawings, in which:

3,059,231 Patented Oct. 16, 1962 ice FIG. 1 is a front elevation of an enclosure of the explosion resistant type with the pilot light device of the present invention installed thereon;

FIG. 2 is a front end elevation of the pilot light device and a fragment of the wall of the enclosure on which it is supported, with a locking means for latching it in operating positions;

FIG. 3 is a right side elevation of the structure illustrated in FIG. 2, the wall of the enclosure being shown in section for clearness in illustration;

FIG. 4 is a sectional view taken on the line 4-4 in FIG. 2, parts thereof being shown in elevation for clearness in illustration; and

FIG. 5 is a right end elevation of the pilot light device illustrated in FIG. 3.

Referring to the drawings, the enclosure, indicated generally at 1, comprises a hollow body in which electrical equipment is to be contained, this body having a peripheral wall 2 and being open at the top for receiving the equipment. The open top is closed by a closure cap 3 of a type which may be spun securely into place. An enclosure of this type and equipment contained therein are described in a copending application of Don I. Arneberg, Serial No. 769,028, filed October 22, 1958, and the details thereof form no part of this invention.

The wall 2 of the enclosure has one or more threaded passages 4 therein, through which wires from the equipment or device may extend for connecting the device to a circuit of the equipment. Each device has a portion which is accommodated in an associated one of the passages for connecting the device to the wall 2.

The pilot light device comprises an external lens 6 which is concavo-convex and disposed so that its convex face is exposed forwardly. The lens has a central portion 6a in the form of a generally globular segment which terminates rearwardly from the forward face in a frustoconical annular skirt 6b which flares outwardly rearwardly from the rear edge of the lens at approximately 30 to the lens axis.

The lens 6 is disposed within a guard 7 having an annular base 8 With an interior wall portion 9 complementary to, and juxtaposed against, the inner face of the rear margin of the skirt 6b. The guard 7 has forwardly extending arms 10 which terminate at their forward or outer end in a frusto-conical annular rim 11. The arms 10 slope inwardly from the base 8 forwardly of the lens. The arms 10 are spaced apart circumferentially of the guard and are relatively narrow circumferentially of the guard.

The rim 11 is of less diameter than the lens and is so arranged that the entire globular segment portion 6a is rearwardly from the plane of the forward base of the rim. The lens is readily visible forwardly through the rim and between the arms, and is visible laterally through the spaces between the arms.

The rim 11 and arms 10 are disposed in spaced relation to the lens so that shocks due to impacts on the guard are not transmitted directly to the lens.

The lens is held fixedly in the guard by means of an annular lens retainer 12.. The lens retainer comprises a frusto-conical shell 12a and a sleeve portion 12b which may be slip fitted into the interior of the base 8 of the guard 7 and additionally held therein by rolling over the rear edge portion of the rim of the base 8, as illustrated at 13 in FIG. 3. The frusto-conical shell has its smaller base disposed toward the front of the lens and has its outer peripheral surface fitting the interior peripheral surface of the skirt portion 61) of the lens so as to hold the lens firmly in place and provide the necessary fit and length of engaging wall surface endwise of the lens to contain an internal explosion.

Interposed between the lens 6 and the frusto-conical shell 12a and wall 9 and a part of the inner wall of the base 8 is suitable gasket material. This material is applied in slightly flowable condition and later sets after the lens is pressure firmly into place by the retainer 12,. The material preferably is one which though applied as a liquid, solidifies or sets to provide an elastomeric mate- .rial such as a silicone type of rubber. This has advantages in that it will cushion the lens with respect to the engaging met-al parts. Further, because of slight variations or irregularities which may occur between the glass and the metal parts, the material will relieve undue stresses which otherwise might be impressed upon and damage the glass. Other suitable materials for accomplishing this purpose may be employed.

The sleeve portion 13 of the lens retainer is internally threaded for connection to a mounting sleeve 15. The sleeve 15 is externally threaded at 16 for cooperation with the internal threads of the sleeve 13.

The sleeve 15 is also internally threaded, as indicated at 17, for connection to a base 18 of the pilot light device. The base 18 is of electrical insulating material and has a cylindrical sleeve portion 19 which is externally threaded for threaded connection with the threads 17 of the mounting sleeve 15. 'It has a bottom socket containing portion 20.

Mounted within the sleeve portion 19 is a bulb socket 22 into which the base 23 of a bulb B is threadably received. The socket is supported on shoulders 24 in the base by means of suitable bolts 25. Spring lock washers 26 are disposed between the bolt heads and socket 22 to allow limited movement of the socket to compensate for heating and cooling. The bolts extend through the bottom portion 20 of the base. At their outer ends, the bolts are connected to conductor strips 27, respectively, which carry screws 28 for connecting the strips to the wires of an external circuit leading into the enclosure. One strip is connected to the socket and the other to a spring contact 29 for engaging a contact 24 on the end of the bulb B. The base has an electrical barrier 30. It can readily be screwed tightly into the connector sleeve 15 by engaging flats at its margins with pliers or a suitable wrench.

The connector sleeve 15 is externally threaded for threaded engagement with the internal threads of the wall of the associated passage in the wall 2.

With the parts tightly drawn together by their threaded connections, the wires from within the enclosure are pulled outwardly through the passage in the wall 2 thereof and connected by the screws 28 to the strip conductors 27, respectively. Thereupon, the wires and the base 18 are pushed back through the opening in the enclosure wall until the connector sleeve 15 is presented to the casing. Thereupon, the connector sleeve is screwed into the passage in the wall 2 of the casing to the desired distance.

In order to predetermine this distance and to lock the pilot device in the position in the passage in the wall 2, the sleeve 15 is provided with two chordal grooves 31. The grooves 31 are arranged so that when the sleeve 15 is screwed into the wall passage the distance required, those side walls of the grooves which are nearest the base of the assemblage and face forwardly of the device, lie substantially in the plane of the outer face of the wall 2. In this position, a locking plate 32 is installed in the grooves and lies on the wall to which it is secured in fixed position as to prevent rotation of the sleeve 15.

The locking plate comprises a flat strip of metal generally L-shape in the plane or the wall 2 against which it is juxtaposed. The plate has a base 33, arms 34 and 35 extending therefrom which engage the grooves 31. One of the arms, such as 34, is provided with an aperture 36 which registers with a bore 37 in the wall 2 and receives a tapping screw 33 for holding the locking plate against the other face of the wall 2. The plate is so arranged that, when it is fastened by the screw 38, the inner margins of the arms 34 and 35, near their central portions, lie snugly in the chordal grooves 31 and thereby restrain the sleeve from rotation about its axis. Thus, when the sleeve 15 is screwed into the passage the proper distance, the plate 32 is moved so as to slide the arms into the grooves into embracing relation with the sides of the sleeve until the aperture 36 registers with the aperture 37. Thereupon, the sleeve 15 is secured to the wall 2 and prevents rotation and, therefore, removal of the sleeve and the pilot light assemblage.

The threaded connections of the sleeve 15 with the passage in the wall 2 and with the sleeve portion 1? provide tortuous passages of suflicient length to prevent the scape of gases and flashes from the enclosure through the passage or through the device.

Having thus described our invention, we claim:

1. In a combination including a safety pilot light device, an enclosure having a wall with an internallythreaded passage therethrough, said device including a hollow body, a light bulb socket in the body, electrical connectors, means connecting the connectors to the body, means for rendering the body operative to prevent passage of gases through the body from the enclosure to the exterior of the enclosure when the device is mounted in the passage of the enclosure wall, said body being externally threaded and in threaded engagement with the threads of the passage, and extending into the body when in said engagement, said body having at least one chordal slot in a portion at the exterior of the enclosure wall, said slot opening radially outwardly thereof, a locking member, said locking member having a marginal portion received in said slot, and connecting means offset radially from the body and connected to the locking member and to the enclosure securing the locking member in fixed position relative to the body and enclosure, when the marginal portion is in said slot.

2. The combination according to claim 1 wherein the locking member has two spaced fingers, one finger is received in said slot, the other engages the body at the side opposite the slot so as to prevent the one finger from swinging out of the slot outwardly from the body, said locking member has an aperture therein, and the connecting means is a screw extending through the aperture in a direction generally endwise of the body and in threaded engagement with the enclosure wall and connecting the locking member to the enclosure to prevent it from rotating with the body about the axis of the threaded portion.

3. A guard for a pilot light device including a body supporting a socket and bulb and open at one end for access to the bulb, a lens and guard unit connectable to the body for closing the end of the body and protecting the bulb, said unit comprising a concavo-convex lens with a central portion in the form of a spherical segment and a coaxial frusto-conical annular skirt with its smaller base contiguous to the margin of the central portion and flaring outwardly from the smaller base in a direction towards the other end of the body, a guard comprising two coaxial telescoped sleeves with frusto-conical surface portions engaging the opposite outwardly flaring inner and outer faces of the skirt, respectively, and clamping a portion of the skirt therebetween, means fixedly securing the sleeves to each other, one of said sleeves having arms extending from adjacent the skirt in a direction toward and beyond the central portion in spaced relation thereto, and a rim carried by the arms coaxial with and spaced from the spherical segment portion.

4. A guard for a pilot light device including a body supporting a socket and bulb and open at one end for access to the bulb, a lens and guard unit on the body for closing the end of the body and protecting the bulb, said lens being concave-convex and having a central globular segment and a frusto-conical annular skirt extending from the periphery of said segment with its smaller base contiguous with the peripheral margin of the segment, said guard means having clamping means supporting the lens with the segment and a portion of the skirt disposed outwardly beyond the end of of the clamping portion, and said clamping portion having arms extending endwise alongside the outwardly disposed lens portion in spaced relation thereto and spaced from each other circumferentially thereof, and an open rim carried by the arms in coaxial relation to the segment and spaced therefrom both radially outwardly and endwise of the axis of the segment outwardly therebeyond.

5. A guard according to claim 4 wherein said lens and guard unit include a pair of telescopically arranged members having wall surfaces complementary to the external and internal Wall surfaces of the skirt, respectively, and a thin layer of elastorneric material interposed between said external and internal surfaces of the skirt and the complementary wall surfaces of the elements, respectively.

References Cited in the file of this patent UNITED STATES PATENTS 1,010,592 Cole Dec. 5, 1911 1,056,392 Barr et al. Mar. 3, 1913 1,410,007 Downey Mar. 21, 1922 1,425,139 Rumsey Aug. 8, 1922 2,777,942 Lester Jan. 15, 1957 

